No effective system has been devised for maintaining a magnetic element at an equitable position by means of a magnetic field produced by any magnets positioned on one side of a plane, with the levitated element on the opposite side thereof and wherein external forces (e.g. gravity) tending to move the levitated element away from the levitating system are not essential for the equilibrium to exist.
Previous methods for low cost, stable magnetic levitation apply electromagnets mounted above the levitated magnetic element which is subjected to gravity. This configuration is able to provide stability in five degrees of freedom without a feedback control, and a simple feedback control is all that is required to stabilize the element in its vertical position. This system is not effective where an external force, e.g. gravity is not tending to move the element away from the electromagnets.
U.S. Pat. No. 2,323,837 issued Jul. 6, 1943 to Neal describes an attempt at levitating a magnetic element from below. In this arrangement a plurality of magnets are arranged in a circle and the levitated magnetic element is positioned within the circle with like poles of the circular and levitated magnets facing each other. This system has not proved satisfactory, as it is well established that such a system is inherently unstable.
U.S. Pat. No. 3,638,093 issued Jan. 25, 1972 to Ross describes a levitation system that functions also as a linear electromagnetic electric motor which supports the driven element above a track.
U.S. Pat. No. 4,585,282 issued Apr. 29, 1986 to Bosley shows a system for levitating a magnetic element from above with various feedback controls that may be employed to ensure stability of the levitated element. This patent also describes a possible technique for levitating an element and maintaining it in a stable position by means of levitating magnets positioned below a plane. This system has not proven satisfactory, possibly because the levitated object is unstable in two degrees of freedom, which makes feedback control for stabilization difficult.